Protective relay



us- 1951 w. E. GLASSBURN 2,565,127

PROTECTIVE RELAY Filed Feb. 16, 1950 1 I AVAVAL 1 A AVA B Ayl1l c o@ 5wJ wJ wJ 3o ""1 "1 ""1 WITNESSES: INVENTOR William E. Glossburn.

72w M w Patented Aug. 21, 1951 UNITED STATES PATENT OFFICE PROTECTIVERELAY William E. Glassburn, Bloomfield, N. J., assignor to WestinghouseElectric Corporation, East Pittsburgh, Pa., a corporation ofPennsylvania Application February 16, 1950, Serial No. 144,401

' 12 claims, (01. 175 294) said overcurrent element from producing anytorque when the directional-element contact is open.

It is the principal object of my present invention to producean improvedhigh-speed directional overcurrent relay in which the overcurrentelement is so controlled by a directional element that the direction ofthe torque or operatingforce which is produced in the overcurrentelement actually reverses, dependentupon the position of thedirectional-element contact.

The system-conditions under which my new relay-control is needed, andthe nature and structural design of my improved relay. will behereinafter described and claimed, with reference to the accompanyingdrawing, wherein the single figure is a diagrammatic view of circuitsand apparatus illustrative of a suitable form of embodiment of myinvention.

In the drawing, I have illustrated my invention as being embodied in aphase-A relay which is used in the protection of a three-phasetransmission or distribution line I. The line is connected to astation-bus 2 by means of a circuitbreaker 3 which is provided with anauxiliary breaker-contact 3a and a trip coil TC. Linecurrent forrelaying purposes is derived by means of a bank of line-currenttransformers 4, and line-voltage for relaying purposes is derivedrbymeans of a bank of potential transformers 5.

My relaying apparatus, as illustrated, comprises a directional elementD, which responds to the direction of the line-current I in phase-A ofthe line I, and an overcurrent element HR which responds to apredetermined magnitude of the line-current I. Both of theserelay-elements D and HR are of the product-responsive type, by which Imean the type of relay which develops a torque or operating-forcewhichis proportional to the product of two single-phase fluxes,multiplied by a function of the phase.- angle or time-phase betweenthem. This prod- 2 net-responsive effect can be produced, either in adifierential type of relay in which either the operating force or therestraining force is responsive to the resultant of two out-of-phasecurrents or fluxes, as illustrated in the Goldsborough Patent 2,404,955,granted July 30, 1946,, or it. can be produced in a wattmetric type ofrelay in which the stator-member has two fluxproducing windings forproducing two interacting single-phase magnetic fluxes having poleswhich are displaced spatially relative to each other, and a rotor memberwhich is so disposed as to produce a torque which is proportional to theproduct of these two single-phase fluxes multiplied by a function of thetime-phase between them, an illustrative example of such wattmetric-typerelay being shown in the previously mentioned Hoard patent.

In the drawing, the directional element'D is illustrated as having acurrent-winding II, a voltage-winding l2, and two sets of make-contactsl3 and I4. The current-winding H is shown as being energized by theline-current I, as derived by the line-current transformer 4. Thevoltage-001112 is ,il1ustrated as being energized from-the, phase ABvoltage, as derived by the potentialdtransformers 5, with, a resistanceR, in. series with .said voltage-winding l2.

The overcurrent relay HR is illustrated as havingtwo current-responsivewindings 2| .and 22,

and a make-contact |5. Some dephasing means should be associated inshunt-circuit relationto one of the windings, such as 22 of theovercurrent element I-1R,,so that the fluxes which are produced, by thetwo windings 2| and 22 of this relay shall, not both bear the sametime-phase relation to the energizing-currents which are su'pplied tosaid windings,.when said windings are connected together in series witheach other. The dephasingr means which I have illustrated for thispurpose is a short-circuited lagging-coil 23., In a broader sense,however, such laggingcoil means should be construed as beingrepresentative of any. means which causes the two fluxes of theovercurrent relay HR to be dephased with respect to each other when thetwo currentwinding circuits are connected in series with each other, sothat the fluxes are neither in exact phase with each other or in exactphase-position. In theillustrated form of embodiment of my invention,the two, current-coils 2| and 22 of overcurrent element HR. have acommon terminal 24, These two current-coils 2| and 22 are providedlwithseparate energizing-circuits 3| and 32, respectively,branchingback from said com- 3 mon terminal 24, the other terminals ofthese two separate energizing-circuits being indicated at 3| and 32,respectively.

I provide an auxiliary current-transformer 33, having a tapped-changingprimary winding 33 which is energized by the line-current I in serieswith the current-winding I I of the directional element D. Thetransformer 33 is shown as having a separate secondary Winding 34,although an autotransformer could have been used, with the same windingserving as both the primary and the secondary windings. The secondarywinding 34 has terminals 3| and 34, and these terminals 3| and 34' serveas thetwo terminals of a single-phase voltage-source which is used toenergize the energizing-circuits 3| and 32 of the two current-windings2| and 22 f theovercurrent element HR. The secondary winding 34 has anintermediate tap 32', so that this secondary winding 34 serves broadly,in efiect, as an impedance-means having the two terminals 3| and 34',and an intermediate tap 32. The supply terminals 34 is connected to thedirectional-element contact l3, and thence to the common terminal 24 ofthe two current-coils 2| and 22 of the overcurrent element HR, while theother terminals 3| and 32 of the current-coils 2| and 22, respectively,are connected to the other sourceterminal SI of the secondary winding34, and to the intermediate secondary tap 32', respectively.

The tripping-circuit is shown as being connected from a positivebattery-terminal through the make-contact I5 of the overcurrent elementHR, and the make-contact M of the directional element D, and thence tothe trip coil TO, the circuit being completed by the auxiliarybreaker-contact 3a and the negative battery terminal The polarities ofthe connections of the overcurrent element HR are such that this element1 develops a contact-closing torque when the flux produced by theunshaded coil 2| leads theflux produced by the shaded coil 22 by acertain angle such as 45. This condition is produced when both of thesecoils 2| and 22 are energized in the same polarity, which is the casewhen the directional-element contact I3 is closed. In such a case, thecoil 2| is impressed'wit-h a voltagerfrom 3 to 34, and while the coil22is impressed with a substantially in-phase, but smaller, voltage from32' to 34. When the directional-element contact l3'is open, however, thetwo coils 2| and 22 are connected in series with each other, across thevoltage from 3'|"to 32', so that the polarity of the coil 22 isreversed. The impedances of the two coils 2| and '22may conveniently bedesigned so that they have the same impedance-angles, although thisdesign-condition is not necessary.

As a result of the above-described connections, my overcurrent elementHR has a restraining or contact-opening torque, when thedirectionalelement contact I3 is open, and said overcurrent element hasan operating or contact-closing torque when the directionalelementcontact I3 is closed. The contact-opening torque of the overcurrentelement is in addition to any relaybias which may be provided, forbiasing the relay toward its open or non-responsive condition, asindicated at 40. My relay is designed so as to have its negativeorcontact-opening torque when the directionalelement contact I3 is open,in order toj avoid a possible erroneous relaying operation on the pro.-tected line I. It will be understood that the di- Iectional element D ismore sensitive than the 4 overcurrent element HR, so that thedirectional element D responds to the direction of the linecurrent I, orto the phase of this line-current with respect to the line-voltage inphase AB, without attempting to discriminate between heavy currents andlight currents, or between fault-currents and load-currents. Thedirectional element D thus responds to the direction of the loadcurrentsWhich-are flowing in the line I when there is no fault-condition. Theovercurrent element HR, on the other hand, is designed to pick up, orrespond, or close its contact I5, only when the magnitude of theline-current I is sufficient to indicate a fault-condition asdistinguished from the maximum load-current which the line carries.

When the line-current I is flowing into the protected line-section awayfrom the stationbus 2, the directional element D responds, and closesits contacts l3 and. Under these conditions, that is, during normalload-conditions, when there is; no fault-on the protected linesection I,but with theload-current-I flowing away from the station-bus 2, asindicated by the current-arrow I,'the directional-element contacts l3and I4 will both be closed, and the overcurrent element HR will developa torque in the currentclosing direction, but this torque will not besufficient to overcome the forceeof the biasing spring 46, so that theovercurrent-element contact l5 remains open. If,now,-an internal faultoccurs, that is, a fault having a'current flowing in the trippingdirection, the-currentI in the protected line-section reaches amagnitude sufficient to cause the overcurrent element HR to close itscontact |5, thus instantly tripping the trip-coil TC, because thedirectional-element contact |4is already closed, since the line-currentimmediately preceding the fault was inthe tripping direction.

' Now, still assumin that the load-current I is flowing in thetrippingdirection, that is, out into the protected line-section I, let us assumethat an external-fault occurs,;which may be on the station-bus 2; orsomewhere on the system back a of this station-bus 2, so that thefault-current now reverses and flows back towards the sta tion-bus 2;When such a fault occurs, the overcurrent element HR'will'at first be inan energized condition in which it develops an operating torque, sothatit will start to close its contact l5. The directional element D,atthe same time, will start to open its'contacts l3 and M, which hadbeen closed, because of 'the direction of flow which was assumedfor theload-current immediately p'revious to the fault. A proper coordinationof the'contacts can easily be managed, by the 'propersetting of thecontact-follow: and travel, so that theidirectional element D will beableto get its closed contacts l3 and I4 open before, the overcurrentelement HR can travel far enough to close its contact l5; thuspreventing. tripping, which is thedesired result when the rfault+currentis in the non-tripping direction.

Such an,externallfaultfhowever, willhave to be cleared bysomeyotherprotective relaying de-, vices (notshown) which are designed to respondto faults Occurringwithin the. place where the assumed fault isilocated,andjwhen these other protective relaying devices respond, and cause avcircuit interruptin operation somewhere else in response, to the fault,the faultvmight be cleared, while the overcurrent-element contact |5vis-still closed, or,whil e the overcurrent element HR is still drifting,by its own inertia, in the contact-closing direction. As soon as theex-.

shown in Fig. 3 of the previously mentioned Hoard patent, where theovercurrent element was merely deenergized, not reversed in torque, inresponse to an opening of the directional contact [3, there wasconsiderable danger that the overcurrent element would continue to driftinto its closed-contact position, after the directional contact 13 hadinitially opened. In my system, however, the opening of the directionalcontact l3 does not merely deenergize the directional element HR, orkill its contact-closing torque, but it actually reverses the torque ofthis overcurrent element, so that this reversed torque will act againstthe inertia which tends to cause said element to continue to move in itscontact-closing direction after the directional contact l3 has opened.The result of my reversed torque is thus a great reduction in thepossibility of the incorrect tripping which would result if theovercurrent contact 15 should be closed at the in stant when theexternal fault was cleared by other means (not shown), and when thedirectional contact I4 should reclose in response to a load-currentflowing in the tripping direction.

If the load-current is in the non-tripping direction, that is, out ofthe protected line-section, and toward the station-bus 2, there will bea proper operation for all faults within the sensitivity of theelements, because the load-current causes the directional contacts l3and [4 to be open. An internal fault will first cause the directionalcontacts 13 and I4 to close, after which the overcurrent element HR willdevelop a torque in the contact-closing position and will close itscontact 15, thus producing a tripping operation. If the fault is in thenon-tripping direction, the directional contacts 13 and I4 willremainopen, the same way they had been in response to the loadcurrent, and thetorque of the overcurrent element HR will remain in the contact-openingdirection so that the overcurrent contact l5 will not close.

While I have described my invention, and explained its method of designand operation, with reference to but a single form of embodiment, I wishit to be understood that the chosen embodiment is only illustrative, andthat my invention is susceptible of various changes by way of thesubstitution of equivalent parts or the addition or omission of partsand refinements. I desire, therefore, that the appended claims shall beaccorded the broadest construction consistent with their language.

I claim as my invention:

1. In combination: a single-phase productresponsive relaying elementhaving contactmeans, two flux-producing winding-means for producing twointeracting single-phase magnetic fluxes which are so disposed as toproduce a force which is proportional to the product of the twosingle-phase fluxes multiplied by a function of the time-phase betweenthem, and an energizing-circuit for each of said windin -v means, thetwo energizing-circuits having one terminal in common; in combinationwith a single-phase voltage-source having two terminals, animpedance-means having two terminals and an intermediate tap, the twoterminals of the impedance-means being connected to the two terminals ofthe voltage-source, means including a circuit-making and -breakingdevice for causing the common terminal of said two energizingcircuits to.be either connected to one terminal of said impedance-means ordisconnected from said impedance-means, and circuit-means for connectingthe other terminals of the respective energizing-circuits to the otherterminal and the intermediate tap, respectively, of saidimpedance-means.

2. A high-speed directional overcurrent relay adapted for use on analternating-current system and characterized by having an overcurrentelement as defined in claim 1, and a directional element for respondingto the phase of a line:- current with respect to a line-voltage, saiddirectional element being operatively associated with the circuit-makingand -breaking device referred to in said claim 1.

3. In combination: a single-phase productresponsive relaying elementhaving contactmeans, and two windings having one terminal in common; incombination with a tapped singlephase energizing-source having twoterminals and an intermediate tap, means including a circuit-making'and-breaking device for causing the common terminal of said two windings tobe either connected to one terminal of said source or disconnected fromsaid source, and circuitmeans for connecting the other terminals of therespective windings to the other terminal and the intermediate tap,respectively, of said source.

4. A high-speed directional overcurrent relay adapted for use on analternating-current system and characterized by having an overcurrentelement as defined in claim 3, and a directional element for respondingto the phase of a linecurrent with respect to a line-voltage, saiddirectional element being operatively associated with the circuit-makingand -breaking device referred to in said claim 3.

5. In combination: a single-phase productresponsive relaying elementhaving contactmeans, two flux-producing winding-means for producing twointeracting single-phase magnetic fluxes which are so disposed as toproduce a force which is proportional to the product of the twosingle-phase fluxes multiplied by a function of the time-phase betweenthem, and an energizing-circuit for each of said windingmeans, the twoenergizing-circuits having one terminal in common, said winding-meansand their respective energizing-circuits being so related that thetime-phase between the flux produced by one winding-means and thecurrent carried by its energizing-circuit is different from thetime-phase between the flux produced by the other winding-means and thecurrent carried by its energizing-circuit; in combination with asingle-phase voltage-source having two terminals, an impedance-meanshaving two terminals and an intermediate tap, the two terminals of theimpedance-means being connected to the two terminals of thevoltage-source, means including a circuit-making and -breaking devicefor connecting the common terminal of said two energizing-circuits toone terminal of said impedance-means, and circuit-means for conn'ectingthe other terminals of: therespective energizing-circuits to :the otherterminal and the intermediate tap, respectively, ofsaidflimpedance-means. 7 6. A high-speed directional overcurrent relayadapted for useon an alternating-current system and characterized byhaving an overcurrent element as defined in claim 5, and .a directionalelement for responding to the phase ofa linecurrent with respect to aline-voltage, said. directional. element being operatively. associatedwith the. circuit-making and breaking device referred to insaid claim 5.

7. In combination:' a singlesphase product-responsive relaying elementhaving contact-means, two windings vhaving one terminal in common, anddephasing means associated with at least one of said windings; incombination with a tapped single-phase energizing-source'having twoterminals and an intermediate tap, means including a circuit-making and-breaking device for connecting the common terminal of said two windingsto one terminal of said source, and circuitmeans for connecting theother terminals of the respective windings to the other terminal and theintermediate tap, respectively, of said source.

8. A high-speed. directional overcurrent relay adapted for use on analternating-current system and characterizedby having an overcurrent element as defined in claim 7, and a directional element for responding tothe phase of a line-current with respect to a line-voltage, saiddirectional element being operatively associate-d with thecircuit-making and -breaking device referred to in said claim '7.

9.- In combination: a single-phase product-responsive relaying elementhaving contact-means, two windings having one terminal in common, anddephasing means associated in shunt-circuit relation to at least one ofsaid windings; in comminal of said two windings to one terminal of saidsource, and circuit-means for connecting the other terminals of therespective windings to the other terminal and the intermediate tap,respectively, of said source.

g ment for responding to the phase of a line-current with: respect to aline voltage, said directional element being operatively associated withthe cir- 'cu'itsmaking' and -'breal ing device referred to in said.claim 9.

11..1A directional overcurrent relay adapted fornuse on analternating-current system and characterized by having a directionalelementfor responding to the phase of a line-current with respect to aline-voltage, an overcurrent element having two windings in suchoperative relation-to each other that the overcurrent element developsacontact-opening force or a contact-closing force dependent upon therelative directions of the currents traversing said windings, and meansunder the control of said directional element for causing the twowindings of said overcurrent element to be energized in onephase-relation when the directional element. is in one position, and forcausing said two windings of the overcurrent element to be energizedin-a 10. A high-speed directional overcurrent relay adapted for useon'an alternating-current system and characterized by having anovercurrent element as'defined in claim 9, and a directionalelesubstantially different phase-relation when said directional elementis in its other position.

12. A directional overcurrent relay adapted for use onanalternating-current system and characterized by having a directionalelement for responding to the phase of a line-current with respect to aline-voltage, an overcurrent element having two windings in suchoperative relation to. each other that the overcurrent element developsa contact-opening force or a contact-closing force dependent upon therelative directions of thev currents traversing said windings, and meansunder the control of said directional element for causing the twowindings of said overcurrent element to be energized in substantiallythe same polarity when the directional element is in one position, andfor causing said two windings of the overcurrent element to be energizedin the opposite polarity, one with respect to the other, when saiddirectional element is in its other position.

WILLIAM E. GLASSBURN.

REFERENCES CITED The following references are of record'in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,379,905 Hoard July 10, 1945 I2,432,328 Morris Dec. 9, 1947

